1. Technical Field of the Invention
The present invention is related in general to the field of telecommunications. More particularly, the present invention is related to a system and method for effectuating selective triggerless local number portability in a telecommunications network having a cellular network portion and a wireline network portion.
2. Description of Related Art
Local number portability (LNP) is typically regarded as the capability of a telephony subscriber to change a service provider without a change in the subscriber""s directory number. LNP is currently possible in most wireline and cellular telephony networks.
Number portability significantly impacts call routing in the existing telecommunications network. This is so because calls between telephone subscribers in the United States are established on the basis of a national directory number plan, wherein each subscriber line is identified by a ten-digit directory number having both geographic and central/end office (CO/EO) switch significance. The ten-digit directory number comprises a three-digit area code (generally denoted by the letters xe2x80x9cNPAxe2x80x9d) defining a specific geographic region, which is followed by a three-digit office code (denoted by the letters xe2x80x9cNXXxe2x80x9d) identifying a particular switch in the network. The office code is followed by a four-digit subscriber line identifier (denoted by the letters xe2x80x9cXXXXxe2x80x9d) establishing the line address of a particular subscriber line served by the switch that is identified by the NXX digits of the directory number. Subscribers who change service providers, for example, while retaining their directory number are served by a switch which normally serves NPA-NXX digits different from the NPA-NXX digits of the subscriber""s directory number. In other words, such subscribers are deemed to have xe2x80x9cportedxe2x80x9d their directory numbers.
Various techniques exist for facilitating the proper call treatment by the network with respect to such ported directory numbers. Techniques also exist that provide for call treatment with respect to calls that are originated in the cellular network but terminate in the wireline network, and involve ported directory numbers. In such scenarios embracing both wireless and wireline networks, a Mobile Switching Center (MSC) is provided with the capability to route the calls to wireline elements such as an Access Tandem (AT), an EO switch, or both, based on Destination Point Codes (DPCs) associated with the calls. The wireline network elements query an LNP database (i.e., xe2x80x9ccall dippingxe2x80x9d) to determine proper call treatment for the ported directory numbers. In essence, a Location Routing Number (LRN) is determined from the database which resembles a traditional ten-digit directory number, wherein the first six digits of the LRN identify a single EO switch in the network. Unlike conventional directory numbers, however, the remaining four digits do not identify a subscriber line address but, instead, indicate that a signaling message parameter should be accessed to obtain the address.
The wireless network may also engage in what is known as a xe2x80x9ctriggerlessxe2x80x9d LNP (TLNP) processing wherein LNP database queries are not initiated by the MSC. Instead of dipping the call, the MSC sends normal signaling messages to the wireline network via a Signaling Transfer Point (STP) that has the TLNP capability. When invoked, the TLNP capability inspects messages sent from the MSC to the wireline network. Specifically, the STP intercepts Signaling System No. 7 (SS7) messages (Initial Address Messages or IAM), and uses information obtained from the message to perform an LNP query. Upon query response, the TLNP capability modifies the IAM with the appropriate LNP information and sends the message to its destination. When the wireline network receives the message, it processes it according to normal LNP procedures for a message that has been LNP-dipped.
As is well known, many MSCs have more than one trunk group for routing calls associated with a particular NPA-NXX. For example, an MSC may route a call to the AT disposed in the wireline network portion over what is known as a Type 2A connection. Further, the MSC may route a call to the EO switch via a Type 2B connection. In either routing methodology, TLNP processing at the STP may be provided with respect to directory numbers in LNP environment.
Certain problems arise when an LNP-dipped call for a ported number is forwarded to an EO switch when the ported number is served by a different switch. Since the receiving EO switch typically cannot forward LNP-dipped calls when an LRN is present indicating a ported number, the calls get dropped. Additionally, this problem is particularly compounded when the MSC is in some service agreement to route as much of call traffic as possible to a particular EO switch over a Type 2B connection.
Based on the foregoing, it should be appreciated that there has arisen a need for a modified TLNP process wherein an MSC can route dipped calls to the AT node using normal TLNP procedures, while selectively engaging in the TLNP processing only for calls routed to the EO (via Type 2B connections) with respect to directory numbers that are identified as ported into that EO.
Accordingly, the present invention provides an innovative system and method for effectuating selective triggerless local number portability (TLNP) processing in a telecommunications network having a cellular network portion and a wireline network portion. By practicing the teachings of the present invention, communication traffic from a Mobile Switching Center (MSC) disposed in the cellular network portion can be selectively LNP-processed to minimize the cost of implementing LNP procedures on such traffic.
In one aspect, the present invention is directed to a method for effectuating selective TLNP in a network as set forth above. When an Initial Address Message (IAM message) is received from the MSC on a TLNP-enabled link set, a determination is made at a Signal Transfer Point (STP) associated therewith whether the NPA-NXX of the received dialed number is marked as portable. If not, the TLNP processing is discontinued and the message as originally received is forwarded to the wireline network portion for further processing. Otherwise, another determination is made to see if the dialed number is a ported number. If it is determined that the dialed number is not a ported number, the IAM message is marked as dipped and forwarded to the wireline network portion based on the Destination Point Code (DPC) associated with the message. On the other hand, if the dialed number is a ported number, a further determination is made if the DPC of the message corresponds to a match in a DPC/LRN database table. If the DPC is not in the DPC/LRN database table, the TLNP processing is applied to the message before it is forwarded to the wireline portion based on the DPC of the message. If the DPC is in the DPC/LRN database table, it is yet further determined whether the LRN received from the database query corresponds to a match in the DPC/LRN database table. If the LRN is not in the DPC/LRN database table, the message is forwarded, again as originally received, to the wireline network portion. Otherwise, the TLNP processing is applied to the message before it is forwarded to the wireline portion based on the DPC.
In another aspect, the present invention is directed to a system for effectuating selective TLNP in a telecommunications network having a cellular network portion and a wireline network portion. The cellular network portion includes an STP that is operable to receive a plurality of IAMs (which include the dialed numbers of called parties disposed in the wireline network portion) from an MSC on a TLNP-enabled link set to which it is coupled. The MSC includes a structure for forwarding the IAM messages to the STP which preferably includes a TLNP database. The database is populated with a NPA-NXX table for identifying portable NPA-NXX numbers and DPC/LRN decision tables. The wireline portion includes a plurality of EO switches within a number portability area and one or more Access Tandem (AT) nodes. Trunks from the MSC to the wireline network portion comprise Type 2A connections to the AT nodes as well as Type 2B connections to select EO switches with which the MSC operator has service agreements to forward call traffic. A logic structure is operably associated with the STP for determining whether the communication traffic received at the STP over a select TLNP-enabled link of the cellular network portion is to be selectively processed for TLNP procedures, wherein a portion of the traffic is directed to a select EO switch (e.g., EO-1) over a Type 2B connection. The determination is based on queries to both NPA-NXX tables as well as the DPC/LRN decision tables. For calls that terminate in the EO-1 switch and calls to be ported into that switch, the IAM messages are marked as dipped. On the other hand, for the ported calls for which the LRN does not match the LRN of the EO-1, the IAM messages are routed to the wireline network portion without any dipping flags.
In yet another aspect, the present invention is directed to a computer-accessible medium operably associated with a processing entity located at a signaling node (such as, e.g., an STP with an LNP database) that is disposed in a telecommunications network. The computer-accessible medium carries a set of instructions which, when executed by the processing entity, cause the signaling node to perform the steps of a selectively effectuated TLNP processing method such as the method set forth above, in order to maximize call traffic forwarded on Type 2B connections while minimizing the cost of implementing TLNP on such traffic.